A typical trenching machine includes a boom assembly mounted on and extending from a frame of the trencher machine. The boom assembly is mounted for movement between a transport position and a digging position. The boom assembly includes an endless digging chain and tooth assembly which orbitally rotates during operation of the machine to dig a relatively narrow trench in the ground.
A drive sprocket is typically provided toward a first end of the boom assembly for controlling the operational speed of the digging chain and tooth assembly. The digging chain and tooth assembly is entrained about and rotatably supported by the drive sprocket.
The boom assembly further includes a boom which extends away from the drive sprocket and has the digging chain and tooth assembly arranged for orbital movement thereabout. A boom end idler assembly is normally provided toward a free end of the boom for further supporting the digging chain and tooth assembly. The boom end idler assembly includes a boom end idler having a diameter considerably larger than the drive sprocket to reduce chain roller wear as the chain of the digging chain and tooth assembly rotates thereabout.
Boom assemblies equipped with larger diameter boom end idlers at the free end thereof usually include a boom configured as a hollow housing with laterally spaced side walls arranged on each side of the boom end idler and having top and bottom walls joining the side walls. The top and bottom walls of the boom housing support extended reaches of the digging chain and tooth assembly and inhibit rocks and the like from becoming entrapped between the digging chain and tooth assembly and the boom.
Some trencher manufacturers utilize anti-friction bearings such as roller bearings centrally accommodated within the boom end idler to mount and facilitate free rotation of the boom end idler about the boom. Conventional roller bearings include rolling members between inner and outer races to significantly reduce the rotational and frictional drag of the boom end idler about its rotational axis and thereby reduce the power required to drive the chain and tooth assembly.
To further reduce frictional drag on the boom end idler as it rotates, the lateral space between inner surfaces of the side walls of the boom housing is greater than the width or thickness of the boom end idler. Thus, the boom end idler assembly is substantially free to rotate therebetween. As a result of such construction, however, there is a lateral space or opening between the boom end idler and each of the side walls of the boom housing. As will be appreciated, trencher manufacturers try to minimize the opening or space between the boom end idler and the boom housing.
As the digging chain and tooth operates, there is an abundance of mud, dirt, stones, rocks and other foreign debris circulating about the boom assembly. Such dirt, mud and other foreign debris presents a serious problem to boom assemblies using boom end idlers in that such foreign debris tends to move through the space or opening between the boom end idler and the boom housing and gets into the bearing area and contaminates the bearing. As will be appreciated, the dirt and other debris acts to sometimes seize and/or quickly destroy the bearing thus requiring repair or replacement thereof.
Some anti-friction bearing include seals on opposite sides of the rolling members between the inner and outer races of the bearing. Although adding cost to the bearings, such seals do not prevent dirt, debris and other foreign matter from moving through the openings between the boom end idler and the boom housing and toward the bearing. As a result such seals are quickly destroyed by the contaminants in the working environment. The beneficial results obtained from use of anti-friction bearings is therefore quickly lost due to the down time associated with repair or replacement of the bearings resulting from contamination thereof by the environmental conditions in which the boom assembly is typically operated.
Thus, there is a need and a desire for a trencher boom assembly having a boom end idler which is mounted to a boom by anti-friction bearings which are sealed to the environment in which the boom assembly normally operates.